Rousseff had 51 percent of valid votes, compared with 31percent for former Sao Paulo state Governor Jose Serra in asurvey by pollster Ibope, according to the Globo network'swebsite. A survey by the Datafolha firm showed her winning 50percent, compared with Serra's 31 percent, Globo said on itswebsite.

Rousseff needs more than 50 percent of votes to avoid arunoff on Oct. 31. (Editing by Peter Cooney)